This species is very similar to G. l i a t and is therefore not redescribed in full. Only differences from the new species are listed, and these are primarily in the thoracic color pattern and the male and female terminalia.

Head: No significant differences between the species were observed.

Thorax ( Figs. 5
View Figure
, 7
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): Dark thoracic pattern similar to G. liat but somewhat reduced compared to it. Dark median mesonotal vitta in G. wiedemanni conspicuous only on posteror half of scutum or less, whereas on anterior half this vitta yellow, barely distinguishable from yellow background, at most with small dark spots or streaks primarily in areas lacking microtrichia; branching of vitta not obvious, and shiny black lateral spots, extending from postpronotal lobe to base of wing, disconnected from median vitta. Scutellum posteromedially around apex with 3 usually isolated black spots ( Fig. 5
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). Single squarish or oval large dorsomedian spot, similar to but slightly narrower than posterior broadening of median vitta (over scutoscutellar suture), and small round spot each around base of apical scutellar seta, at margin of scutellum; these 3 spots sometimes more or less merge with each other, but even in extreme cases small but conspicuous yellow mark obvious in middle of united black spot (no such yellow mark in G. l i a t). Pleural pattern ( Fig. 7
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) differs from that of G. l i a t by dark vittae being weakly contrasted with yellow or ivory-white background, if present at all; these vittae usually yellow or brownish-yellow, and black or blackish areas reduced to small rounded blackish spot posterodorsally on katepisternum, and to similar spot in middle of meron; both spots with diameter smaller than length of crossvein R-M. Group of such small blackish areas present dorsal and anterior to base of halter. The only exception was found in the three specimens from Rheinland, Germany (see material examined) in which these dark spots are larger, especially large triangular spot occupying most of katepisternum.

Wing: No significant differences were noted between the wing pattern and venation of the two species.

Abdomen: Yellow to brown, without black bands; tergites 2–4 in male, 2–5 in female, with golden-yellow microtrichia either completely covering tergites or only their posterior margins; only last tergite bare and shiny.

Male terminalia: Epandrium: No significant differences from G. l i a t have been noted. Phallus ( Fig. 12
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): Bubble-like structure smaller than in G. liat, about as long as sclerotized part anterior to it.

Distribution ( Fig. 24
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). The Palaearctic catalog ( Foote, 1984) states: Central and southern Europe (not including Scandinavia), Central and south-western Russia, Israel, North Africa. However, the record of Israel is based on a misidentification of G. liat, and the record of North Africa is probably based on the unconfirmed record of Séguy (1934) and is therefore doubtful (notice question marks in Fig. 24
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). Other records from Israel ( Freidberg and Kugler, 1989, and Norrbom et al., 1999) are also incorrect as they are again based on misidentifications of G. liat.

Comments. Although very similar to G. l i a t, the only other congener, the characters depicted in the key should allow easy identification for both species.